MySQL 5.6 achieved General Availability (GA) status with MySQL
5.6.10, which was released for production use on 5 February
2013.

MySQL 5.5 achieved General Availability (GA) status with MySQL
5.5.8, which was released for production use on 3 December 2010.

MySQL 5.1 achieved General Availability (GA) status with MySQL
5.1.30, which was released for production use on 14 November
2008.

MySQL 5.0 achieved General Availability (GA) status with MySQL
5.0.15, which was released for production use on 19 October
2005. Note that active development for MySQL 5.0 has ended.

A.1.2:
What is the state of development (non-GA) versions?

MySQL follows a milestone release model that introduces
pre-production-quality features and stabilizes them to release
quality (see
http://dev.mysql.com/doc/mysql-development-cycle/en/index.html).
This process then repeats, so releases cycle between
pre-production and release quality status. Please check the
change logs to identify the status of a given release.

MySQL 5.4 was a development series. Work on this series has
ceased.

MySQL 5.7 is being actively developed using the milestone
release methodology described above.

A multiple-table insert can be accomplished using a trigger
whose FOR EACH ROW clause contains multiple
INSERT statements within a
BEGIN ... END block. See
Section 20.3, “Using Triggers”.

A.1.5:
Does MySQL 5.6 have a Query Cache? Does it work on
Server, Instance or Database?

Yes. The query cache operates on the server level, caching
complete result sets matched with the original query string. If
an exactly identical query is made (which often happens,
particularly in web applications), no parsing or execution is
necessary; the result is sent directly from the cache. Various
tuning options are available. See Section 8.9.3, “The MySQL Query Cache”.

A.1.6:
Does MySQL 5.6 have Sequences?

No. However, MySQL has an AUTO_INCREMENT
system, which in MySQL 5.6 can also handle inserts
in a multi-master replication setup. With the
auto_increment_increment and
auto_increment_offset system
variables, you can set each server to generate auto-increment
values that don't conflict with other servers. The
auto_increment_increment value
should be greater than the number of servers, and each server
should have a unique offset.

A.1.7:
Does MySQL 5.6 have a
NOW() function with fractions of
seconds?

No. This is on the MySQL roadmap as a “rolling
feature”. This means that it is not a flagship feature,
but will be implemented, development time permitting. Specific
customer demand may change this scheduling.

Yes. MySQL is fully multi-threaded, and will make use of
multiple CPUs, provided that the operating system supports them.

A.1.9:
Why do I see multiple processes for mysqld?

When using LinuxThreads, you should see a minimum of three
mysqld processes running. These are in fact
threads. There is one thread for the LinuxThreads manager, one
thread to handle connections, and one thread to handle alarms
and signals.

A.1.10:
Have there been there any improvements in error reporting when
foreign keys fail? Does MySQL now report which column and
reference failed?

The foreign key support in InnoDB has seen
improvements in each major version of MySQL. Foreign key support
generic to all storage engines is scheduled for MySQL 6.x; this
should resolve any inadequacies in the current storage engine
specific implementation.

A.1.11:
Can MySQL 5.6 perform ACID transactions?

Yes. All current MySQL versions support transactions. The
InnoDB storage engine offers full ACID
transactions with row-level locking, multi-versioning,
nonlocking repeatable reads, and all four SQL standard isolation
levels.